1. Field of the Invention
The present invention is directed to optical data transmission systems and, more particularly, to a parallel optical data transmission device which has an array of solid-state light-emitting elements, such as semiconductor lasers, mounted on the same substrate using a hybrid IC technology and transmits optical information signals in a parallel manner.
2. Description of the Related Art
The recent great increase in the quantity of information to be transmitted in a computer communication network makes those skilled in the art hesitate to conclude that the conventional (serial or parallel) electrical signal transmission lines provided among intercomputer communication machines are excellent transmission media whose transmission capability will still be satisfactory even in the future.
The optical transmission technology has been introduced to fulfill the demand of a greater amount of, and faster transmission of, intercomputer information signals. Basically, it is undeniable that the optical transmission technology is given an important role in the highly advanced computer communication network in light of its advantages, such as noninductiveness, wideband characteristic and high-speed transmission of the transmission lines. Those skilled in the art do not however believe that a single optical transmission line employed among the existing communication machines can sufficiently cope with transmission of high rate, digital optical information signals.
The key to overcome these problems is the parallel optical data transmission technology. Data communications among computer terminals, known as "workstations," are normally executed with digital data having a selected number of bits as a data unit, so that the parallel optical transmission scheme is just the "best casting." With the parallel optical transmission scheme, the signal transmission capacity and the signal transfer rate can be significantly increased; in addition, it is possible to in principle eliminate the need for extra circuit structures, such as parallel-to-serial converters and time-division multiplexing/demultiplexing devices, unlike in the case of serial transmission using a single transmission line path, and, at the same time, to minimize the total required buffer memory. This can reduce the burden on the hardware structure.
The parallel optical transmission technology, which is expected to be prosperous, actually has several unsettled issues. One of these issues is realization of perfect unification of effective wire lengths at the electric wiring portions of individual signal transmission channels. Another issue is to deal with reduction in effective signal margin caused by the inductive cross talk between adjoining electric signal transmission channels and/or ground potential noise and elimination of the non-uniform characteristic impedance. These shortcomings are hindering parallel optical transmission from being applied to computer communication systems, and there is a strong demand of promptly solving the problems.